desert bluegrass
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Joined: Mon Jun 03, 2013 2:31 am
Location: Terlingua, TX

Pesticide for tender seedlings

I'm looking for an insect solution. I have a small indoor seed starting tray/cloche kit with a grow light. The grow light sits atop the clear plastic cover directly over the seed pots. Unfortunately, the grow light attracts insects. I'm not sure how they get into the house but they do and they congregate outside and find their way inside the cloche. They are box elder bugs and some sort of knat. The knats seem to proliferate and I think introduce other parasites or bacteria to the plants. Either way, they are damaging to the seedlings.

I have tried a couple of insecticides but they seem to burn the young and tender leaves. Does anyone have any experience with this issue and know of a seedling friendly insecticide that can be used successfully?

Thank you.

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Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

I would take the set up apart and clean it rather than use pesticides. Clean the entire area, not just the fixture. also check the soil in the pots. If they are fungus gnats, you will probably find them there as well.

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Joined: Thu May 01, 2008 7:21 pm
Location: Zone 6, NJ (3/M)4/E ~ 10/M(11/B)

If the small gnats are black with pointy black/grey striped abdomen, then most definitely fungus gnats and this is pretty much normal when growing indoors. The plastic cover is not needed if the seeds have sprouted and can lead to other fungal issues so it should be gradually removed (not all at once or the seedlings softened by overly humid conditions will dry out). Work on reducing the moisture level in the soil and allow the top surface to feel dry to the touch before watering.

When overwhelming, I do use Bti for mosquitoes which also work on fungus gnats. They are available in liquid solution or impregnated dried stasis form on corn cob bedding or donut shaped floating lump in pond supply or lawn/garden supply. But fungus gnats can be easily trapped with containers of sudsy water (use floral scented shampoo or body wash for best results).
If the box elder (?) bugs are too numerous to pick off by hand, this stinkbug trap rainbowgardener mentioned may work on them too?
Subject: stinkbug invasion
rainbowgardener wrote:Through this winter we've been seeing the occasional stinkbug in our house, maybe one or two a month. But suddenly it seems like a bunch of them must have hatched out somewhere. In the past couple weeks we have killed at least a dozen, maybe more (my partner who does the bug killing duty doesn't tell me how many of them she has dispatched :) )

So last night when it got dark, I set up a stinkbug trap: A large clear glass bowl filled with very soapy water, with a bright light shining directly on it. I used glass because that way the light glows through it. Within the first hour, it had four stinkbugs floating in it. But when I got up this AM, it was still just the same four. So is that all there were? Were there more, but their four dead companions warned them off? or?

But I did notice this AM that the water had a bunch of little blue eggs in it, so presumably one or more of the dead ones was a gravid female. So LOTS of stinkbugs that didn't live to hatch out!

I'm going to try it again tonight with a white plastic bowl. I saw in the fungus gnat thread, someone saying white works best for them. See if there are more of them!

At least it makes me feel safer in the bedroom! They seemed to keep appearing in there and once Jamie had one on her pillow! :shock: euww, euww! If the trap is on, they are more likely to be over there by the light than by us!

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Super Green Thumb
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Location: TN/GA 7b

Also for the fungus gnats, a little cinnamon in the water you water with is helpful. It doesn't kill the gnats, but it is anti-fungal and cuts down on the fungus that they eat. If you don't over do the cinnamon (just a pinch in a pitcher of water) and you don't get the cinnamon powder directly on the seedling leaves, it will not hurt them.

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